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[lesfac]

I have just fitted the prop shafts to my Severn, convinced myself it was wrong and took them back out.
I made the prop shaft holes in the hull as per the RNLI drawings and fitted the shafts.
I have always thought (maybe wrongly) that it is essential that the end of the prop shaft tube inside the hull must be above the water line to avoid water coming up the tube.
It seems that with the prop shafts supplied the only way to get the upper end of the tube above the water line is by fitting it with a sharper upward angle which isn't right either.
Now I am wondering if I was right all along.
Can anyone put me straight on this?
At least I learned how tough P38 filler is but I don't fancy undoing any more installations
Les

[Davenotdone]

Hi Les, i am no expert but my converted Seaport tug runs a short prop shaft almost horizontal. Both the shaft and the motor are under the waterline. The shaft has an oiler tube fitted and topped up with normal engine oil before each run. You may get a tiny amount of water after each run in the hull but that's about it, i have no problems about it at all. Allso your choice of fitting the shafts seams wrong i think. P38 is a non waterproof filler, not a glue / adhesive. Other members will tell you what type of glue you should use as i don't know what your hull is made from.Don't forget to rough up ( file or sandpaper ) and clean the outsides of your tubes to give the glue something to grab onto. Regards, Dave.

[craggle]

Hi Les

The shaft in my Envoy tug is more or less level with the bottom of the keel and that places it about 1.5 inches below the waterline which means the motor is also under the water line.
I put some thinnish grease in the shaft when it was assembled, Tamiya RC car grease I believe it was and I decided to glue a petri dish under the shaft end inside the boat to catch any drips. So far, no water has made it as far as the dish.

Measuring up the shafts on my Severn kit last night, mine will be under the waterline too, I will be leaving them there as I don't really want to alter the angle of the props.

Craig.

[Flundle (Speedline Models)]

Les, this is a copy of my email to you but it might be helpful for others too.
The prop shafts are the correct length and the angle is correct. The inner end of the propshaft is below the WL and yes, you can expect a little leakage but greasing the shaft will keep 99.9% of it out.
To increase the angle of the shaft is wrong on many fronts but remember, Severns roll, a lot,  due to scale effect and the lower the C of G is the better so keep the motors and batteries as low as possible. That's why they are short.

[lesfac]

Thanks for the replies
I am a bit gutted because I was very pleased with the installation I had done until I noticed how low it was.
I wish I had checked here before I ripped it back out.
I had it in my head that it is essential that the tube end is above the waterline to prevent water ingress.
I guess as it is said "A little knowledge is a dangerous thing"
So I know better now. I will redo the installation.
At least I got a new multi tool to aid the extraction.
Thanks for the help and advice
Les